The present invention relates to an optical information recording/reproducing apparatus provided with an objective lens suitable for recording information to and/or reproducing information from an optical disc based on a predetermined standard. More specifically, the present invention relates to an optical information recording/reproducing apparatus provided with an objective lens suitable for information recording/reproducing for a high-recording density optical disc, such as a BD (Blu-ray Disc).
There exist various standards of optical discs (CD, DVD, etc.) differing in recording density, protective layer thickness, etc. Meanwhile, high-recording density optical discs (e.g., BD), having still higher recording density than DVD, are being brought into practical use in recent years to realize still higher information storage capacity. Incidentally, in this specification, the “optical information recording/reproducing apparatuses” include apparatuses for both information reproducing and information recording, apparatuses exclusively for information reproducing, and apparatuses exclusively for information recording.
In general, in order to correct a coma caused when decentering of an objected lens mounted on an optical information recording/reproducing apparatus occurs, a tilt adjustment is performed for the objective lens mounted on the optical information recording/reproducing apparatus during the manufacturing process of the optical information recording/reproducing apparatus in order to correct the coma caused by the decentering. By performing the tilt adjustment, the amount of coma caused as described above can be suitably suppressed. However, optical discs have individual differences, for example, in regard to the degree of warpage and the protective layer thickness. For this reason, there is a case where a relatively large amount of coma is caused due to individual differences of optical discs during the information recording or information reproducing regardless of the fact that the tilt adjustment has been performed. If such a relative large amount of coma occurs, it becomes impossible to form a suitable beam spot on a recording surface of the optical disc.
In order to solve such a drawback, optical information recording/reproducing apparatuses configured to suitably suppress occurrence of a coma due to individual differences of optical discs have been proposed. An example of such an optical information recording/reproducing apparatus is disclosed in Japanese Patent Provisional Publication No. 2006-185563A (hereafter, referred to as JP2006-185563A). The optical information recording/reproducing apparatus disclosed in JP2006-185563A is configured to detect a peak value of a tracking error signal at each of an inner region and an outer region on the optical disc so as to calculate an optimum tilt angle based on an average of the two peak values. In accordance with the calculated tilt angle, the apparatus performs the tilt adjustment for the objective lens. Since, according to JP2006-185563A, an optimum tilt angle is calculated for the optical disc being mounted on the apparatus (i.e., a particular tilt angle for the optical disc being used is calculated), the occurrence of the coma due to individual differences of optical discs is effectively suppressed.